Abstract

Background

Japanese encephalitis virus (JEV) has a significant impact on public health. An estimated
three billion people in 'at-risk’ regions remain unvaccinated and the number of unvaccinated
individuals in certain Asian countries is increasing. Consequently, there is an urgent
need for the development of novel therapeutic agents against Japanese encephalitis.
Nitazoxanide (NTZ) is a thiazolide anti-infective licensed for the treatment of parasitic
gastroenteritis. Recently, NTZ has been demonstrated to have antiviral properties.
In this study, the anti-JEV activity of NTZ was evaluated in cultured cells and in
a mouse model.

Methods

JEV-infected cells were treated with NTZ at different concentrations. The replication
of JEV in the mock- and NTZ-treated cells was examined by virus titration. NTZ was
administered at different time points of JEV infection to determine the stage at which
NTZ affected JEV replication. Mice were infected with a lethal dose of JEV and intragastrically
administered with NTZ from 1 day post-infection. The protective effect of NTZ on the
JEV-infected mice was evaluated.

Findings

NTZ significantly inhibited the replication of JEV in cultured cells in a dose dependent
manner with 50% effective concentration value of 0.12 ± 0.04 μg/ml, a non-toxic concentration
in cultured cells (50% cytotoxic concentration = 18.59 ± 0.31 μg/ml). The chemotherapeutic
index calculated was 154.92. The viral yields of the NTZ-treated cells were significantly
reduced at 12, 24, 36 and 48 h post-infection compared with the mock-treated cells.
NTZ was found to exert its anti-JEV effect at the early-mid stage of viral infection.
The anti-JEV effect of NTZ was also demonstrated in vivo, where 90% of mice that were treated by daily intragastric administration of 100 mg/kg/day
of NTZ were protected from a lethal challenge dose of JEV.

Conclusions

Both in vitro and in vivo data indicated that NTZ has anti-JEV activity, suggesting the potential application
of NTZ in the treatment of Japanese encephalitis.